This invention relates to ignition resistant thermoplastic compositions made with blends of styrene-butadiene-acrylonitrile copolymers (ABS copolymers) and carbonate polymers containing polytetrafluoroethylene and brominated organo phosphorous compounds which act to reduce the susceptibility of such compositions to ignition and/or burning or at least to minimize the dripping of molten polymer when exposed to fire conditions.
Thermoplastic polymers have found extensive commercial application because of their excellent physical properties. These thermoplastic polymers are suitable for the manufacture of molded parts wherein impact strength, rigidity, toughness, heat resistance, and excellent electrical properties are required. However, these polymers exhibit a brief but definite burning time when contacted with an open flame.
U.S. Pat. No. 3,852,393 discloses a flame retardant blend of polycarbonates with ABS resins and a halogenated hydrocarbon flame retardant.
U.S. Pat. No. 4,463,130 discloses a flame retardant blend of polycarbonates with a halogenated flame retardant, polystyrene, polytetrafluoroethylene resins, and a polyphosphate.
U.S. Pat. No. 4,563,496 discloses the use of a combination of halogenated compounds and metal oxides to improve the ignition resistance of blend of polycarbonate and acrylonitrile-butadiene-styrene copolymer (ABS). However, the metal oxides result in the thermal instability of the polycarbonates.
U.S. Pat. No. 4,692,488 discloses a blend of a polycarbonate, a copolymer of styrene and acrylonitrile, triphenylphosphate, and tetrafluoropolyethylene.
The article by Joseph Green "PB-460 and PB-528 Brominated Phosphate Ester Flame Retardants" (Fire Retardant Chemicals Association Meeting, Grenelefe, Florida, March 21. 1988) discloses that PB-460 and PB- a 528 are brominated aromatic phosphate esters with 60-70 bromine and 3-4% phosphorus.
The article by Joseph Green "Brominated Phosphate Ester Flame Retardants for Engineering Thermoplastics" (Fire Retardant Chemicals Association Meeting, San Antonio, Texas, March 12. 1989) discloses that PB-460 is a brominated aromatic phosphate ester with 60% bromine and 4% phosphorus and that when blended with Teflon 6C, polycarbonate resin and ABS resin, the blend has a V-0 UL-94 rating.